Catalytic treatment of hydrocarbons



Jan. 5, 1943. P. L. vr-:LTMAN CATALYTIC TREATMENT OF HYDROCARBONS FiledFeb. '7, 1940 N .mu-h.,

l All oN T, v mi.. .55 Gm G 22E I e w MN I fl Q zal ,m- All, IIQ +2.10 u525ml mzmom ih Q rt w. \1|o Q 23mg ilY mmNzmSh All. zozxm L ozQh PmozoFom Patented Jan. 5, 1943 i CATALYTIC TREATMENT or nrnnocAnBoNsPreston L. Veltman, Fishkill, N. Y., assignor, by mesne assignments, toThe Texas Company, New York, N. Y., a. corporation of DelawareApplication February '1, 1940, Serial No. 317,627 4 claims. `(ol.19e-52) This invention`relates to the catalytic treatment ofhydrocarbons and particularly to theconversion of petroleum hydrocarbonsby contact with solid porous type conversion catalysts in a highlydivided state.

In acordance with this invention the hydrocarbon to be treated issubjected to contact with the catalyst in a reaction vessel wherein the'pressure exerted upon the contact mass is subjected to controlledfluctuation at predeterminedintervals of time.

The invention contemplates a continuous process of catalytic treatmentwherein the hydrocarbon feed is passed continuously through a contactmass. A substantial pressure is maintained within the mass andtemperatures are maintained such that the desired reaction is effected.At relatively s hort intervals of time the pressure is suddenly reducedwithout cessation in the ilow of hydrocarbon feed to the mass. Thereduction in pressure advantageously amounts to only a portion of thetotal pressure imposed upon the catalytic mass, but is sunlcient tocause substantial expansion of the gaseous materials within thecatalytic mass so that the active surfaces of the catalyst particles aresubjected to a periodic scouring action.

The invention has particular application, for example, to the catalyticcracking of hydrocarbons by contact with a porous type of catalyst.

in the form of particles, pellets, or pills, etc. In such treatment amean uid pressure within the range from to 100 pounds per square inchgaugel is usually maintained within the catalytic mass. In accordancewith this invention the pressure is alternately increased and decreasedfrom the mean during the on-stream period. For example, the pressure ismade to fluctuate over a range of around -15 pounds.

While the pressure is increasing the reactants, including gaseousmaterials present, are forced deeply into the pores of the catalystparticles and into the spaces between particles within the contact mass.Upon decrease in the pressure the gaseous materials escape rapidly fromthe pores and voids, thereby'subjecting the surfaces of the catalyst toa sweeping or scouring action. This sweeping action displaces heavyliquid material tending to accumulate on the exposed surfaces of thecatalyst and which liquid, if not removed, is ultimately converted intononvolatile material forming a carbonaceous deposit upon the catalystsurfaces.

It is contemplated also that during increase in the pressure somecondensation of lighter hydrocarbons present occurs and upon reductionin pressure these condensed hydrocarbons flash into vapor, thusaugmenting the expansion and movement' of gases within the pores of theindividual catalyst particles, as well as within the void spaces betweenparticles within the catalyst mass.

An.object,-therefore, of the invention is to effect forced movement ofgases within the individual particles and within the catalyst mass so asto maintain the active surface areas of the catalyst more available tothe reacting hydrocarbons and thus prolong the active life of thecatalyst. A further object is to reduce the amount of carbonaceousmaterial deposited upon the catalyst and thus reduce the frequency ofregeneration or reactivation.

Reference will now be made to the figures of the accompanying drawing inorder to describe the invention more fully. Figure 1 comprises a owdiagram illustrating the application of the process of this invention tothe catalytic cracking of hydrocarbons, while Figure 2 comprises adiagrammatic illustration of the pressure control valve mechanism.

Referring to Figure l, the feed which may be any material to beconverted, such as hydrocarbon gases, vapors, or liquids, is drawnthrough a pi'pe I by a centrifugal charge pump 2 and delivered to aheater 3. In the heater the feed is heated to a suitable temperaturewhich, for example, may be around 950 F. or in the range of around 800to 1000 F.

The heated feed is conducted from the heater 3 to a reaction chamber 4containing the catalyst. The catalyst may be any suitable catalyst forthe reaction involved, such as silicates of alumina and/or oxides ofmetals. The catalyst may comprise activated hydrosilicate of aluminawith or Without other active materials, such as linely divided metals ormetallic-oxides. The catalyst is advantageously in highly divided form,as for example, in the form of particles, pills, pellets, etc.

The feed hydrocarbons may enter the top of the catalyst chamber and passdownwardlyV through the contact mass `contained within the chamber.

The contacted hydrocarbons then pass from the bottom of the reactorthrough a pipe 5 containing a control valve 6 by means of which latterthe pressure is controlled within the reactor l. The control valvemechanism will be referred to later in connection with Figure 2.

The contacted hydrocarbons are discharged into an expansion drum 1 whichis of suilicient size to dampen the fluctuations in pressure occasionedby the operation of the control valve 3. Gases which may tend toaccumulate in the upper portion of the expansion drum 1 can be fuel isdrawn off from the top of the fractionator I3 through a condenser I2 toa receiving drum I3.

Fixed gases may be drawn off from .the top of the receiving drum I3while the liquid condensate is drawn oit through a pipe I4 to astabilizer I5.

In-the stabilizer I5 the more volatile constituents, such as propane andsome butane, are removed as a vapor fraction, while the stabilizedliquid fraction is drawn oi through a pipe I 6 to a nalfractionator I1.f

Inthe fractionator I1 the stabilized hydrocarbons within the desiredboiling range are removed as a vapor fraction through acooler I3 andaccumulated in a receiver I9.

Liquid constituents boiling above the end boil# ing point of the desiredproduct are removed as a liquid fraction from the bottom of thefractionator through a.valved pipe 20, either for recycling or dischargefrom the system.

asoms'at in .these positions, pressure begins to increase within thepipe 5 and causes the diaphragm 39 in the device 3l to rise, therebyopening the contact points 4l and breaking the circuit 4I. As soon asthe circuit 4I is broken.- the spring 45 closes the relief valve 44.

Upon further increase in the pressure -within the 'pipe l the piston 34in the by-pass valve 33 is forced upwardly against theftension of thespring 35 until the port 35 is opened allowing the by pass valve to ventthrough the pipe 31v into the chamber 3 I As the pressure increaseswithin the chamber 3l the diaphragm 33 is raised,'causing the valve '3.to open. A

When the valve 5 opens the pressure within the pipe 5 drops rapidly sothatthe spring 35 pushes the piston 34 downwardly, thus closing the port36. When the port 36 is thus closed gas or other fluid is trapped withinthe pipe 31 and.v the chamber 3I so that the valve 6 is maintained open.With further drop in pressure within the pipe 5 the diaphragm- 39 in thedevice 38 falls, closing the contact points 40 and thereby closing theelectrical circuit 4 I When this circuit is closed the solenoid 43 opensthe valve 44 permitting the uid trapped within the pipe 31 and chamber3I to discharge through pipe 45 to the atmosphere or other zone ofreduced pressure.

Figure 2 illustrates diagrammatically one pos- Y.

sible way in which the pressure control valve 3 may be operated. Asindicated, the control valve 5 is advantageously of the gate-valve type'actuated by means of a diaphragm enclosed within a chamber 3|.

A spring 32, the tension of which may be adjusted, is provided to exerta positive pressure upon the diaphragm 30 suicient to maintain the valve6 normally in the closed position.

A pressure responsive by-pass valve 33 is connected to the pipe 5between the control valve 3 and the outlet from the reactor 4. Thisvalve contains a piston 34 actuated by a spring 35 and also isresponsive to the pressure within the pipe 5. The valve 33 vents througha port 36 into a pipe 31 communicating with the lower chamber 3I of thecontrol valve 5.

Also connected with the pipe 5 between the by-passvalve 33 and theoutlet of the reactor 4 is a pressure responsive contact device 38.Thedevice 33 contains -an enclosed diaphragm 39 which `is responsive tothepressure prevailing within the pipe 5.

The diaphragm 39 is adapted to make and cuit 4I. The electrical circuit4I includes a source of electricity such as a battery 42 and the windingof a solenoid 43.

Upon release of the pressure from the chamber 3| the valve 6`is closedby the spring 32, thus completing the cycle of operations.

In operating the process it is contemplated that thevalve 5 will opensuddenly and'at rela, tively short intervals of time. The interval maybe about 30 seconds or in the range from several seconds to severalminutes, although it 'may be further increased or decreased, as desired.

The opening and closing of the valve 6 should be adjusted so as to causea relatively small drop in pressure. as for example, around 10 to 15pounds, although this may be varied, depending upon conditionsencountered with particular stocks.

By way of example, a mean pressure of around 50 pounds per square inchgauge may be maintained in the reactor 4, while ,the valve 6 is operatedso as to cause the pressure within the retactor to uctuate at intervalsover a range of about 10 to 15 pounds per square inch gauge.

In this way a pressure wave effect isimposed throughout the contact massand upon the individual particles within the mass, causing a substantialchange in the mass-volume relationship of the hydrocarbons within thecatalyst mass, thereby giving rise to the desired periodic sweep ing orscouring action already described.

As previously mentioned, the charge pump 2 is advantageously of thecentrifugal type adapted break the contact points 40 in an electricalcir- The function of the solenoid 43 is to open a relief valve 44 in apipe 45 communicating with the pipe 31 previously mentioned. The valve44 is provided with a spring 46 adapted to close the valve 44 when theelectrical circuit 4I is open.

In actual operation when the control valve 3 is at rst in the closedposition the relief valvel 44 will in the open position.- With thevalves to operate against a fluctuating discharge pres- Sure.

`introduced to the inlet of the heater 3, as indicated, or may beseparately preheated and inltroduced with the heated hydrocarbon feed directly to the top of the reactor 4. v

Obviously many' modifications and variations of Y.

' the invention as hereinbefore set forth may be prevailing in thecatalyst zone Within a relatively narrow range extending both below andabove a predetermined mean pressure, subjecting the pressure in thereaction zone to substantially continuous fluctuation Within said range,'without interrupting the introduction of hydrocarbon feed thereto, thepressure alternately increasing and decreasing from said mean atintervals of from several seconds to several minutes, and discharginghydrocarbon products of conversion from the reaction zone.

2. The method according to claim 1 in which the pressure increases anddecreases over a range of about 10 to 15 pounds.

3. In the catalytic cracking of hydrocarbon oil to produce gasoline, themethod comprising continuously introducing a stream of vaporized feedoil in the temperature range of 800 to 1000 F. to a reaction zonecontaining a mass of solid conversion catalyst in particle formmaintained under cracking conditions, passing the heated feed oil vaporsthrough said mass within the reaction zone, maintaining an absolutepressure prevailing in the catalyst zone within a relatively narrowrange extending both below and above a predetermined mean pressure,subjecting the pressure in the reaction zone to substantially continuous

